A new polyimidazole tripod NN-bis((1-methyl-4-pivalamidoimidazol-2-yl)methyl)-N'-((1-methylimidazol -2-yl)methyl)amine (L2) has been synthesized and shown to form intramolecular hydrogen bonds with different axial ligands bonded to Cu(11) in the solid state, The same hydrogen-bonding property of L2 appears responsible for the stabilization of a Cu(II)-OOH species in solution. The crystal structures of L2 and three of its Cu(II) complexes are reported. The [Cu(L2)X]CIO4 complexes, 4-6 (X- = CI-, OH-, or N-3(-)) have distorted trigonal bipyramidal geometries in the solid state and have been characterized further by UV-vis absorption, electron paramagnetic resonance (EPR) spectroscopy, and cyclic voltammetry. The reaction of [Cu(L2)OH](CIO4) (5) with H2O2 and tert-butyl hydroperoxide in methanol generates [Cu(L2)OOH](CIO4) (7) and [Cu(L2)OO'Bu](CIO4) (8) which have been characterized by different spectroscopic methods. The compound [Cu(L2)OO'Bu](+) displays a band at 395 nm (epsilon = 950 M-1 cm(-1)) assigned to an alkylperoxo pi*(sigma) -> Cu ligand-to-metal charge transfer (LMCT) transition, while (Cu(L2)OOH](+) displays a peroxo pi*(sigma) -> Cu charge-transfer transition at 365 nm with epsilon = 1300 M-1 cm(-1), a mass ion at m/z 593.4, and v(o-o) stretch (resonance Raman) at 854 cm(-1) that shifts to lower energy by 46 cm(-1) upon O-18 substitution.